Mock File IO static class in c#

Question

I am new to Unit Testing, and I need to mock the File static class in System.IO namespace. I am using Rhinomock, what is the best way to accomplish this,

Lets say I need to mock the File.Exists,File.Delete ...

Plenty of examples on this site already, use the search button — ChrisBint, Jun 27 '11 at 22:55
possible duplicate of [Mocking Static methods using Rhino.Mocks](http://stackoverflow.com/questions/540239/mocking-static-methods-using-rhino-mocks) — sarnold, Jun 27 '11 at 22:57
Sometimes people dont know what to search for, perhaps you could give some examples rather than being completely useless. Just a thought. — CrazyDart, Jun 27 '11 at 23:06

score 7 · Accepted Answer · edited May 23 '17 at 11:47

7

You can't mock static methods with Rhino mock. See this question for more info. You could create a facade class to wrap the file system calls you will use and then create a mock version of that.

edited May 23 '17 at 11:47

Community

1
1

answered Jun 27 '11 at 22:56

Don Kirkby

53,582
27
205
286

Rather than make your own facade, use one someone else has already written for you: http://systemioabstractions.codeplex.com/ – vcsjones Jun 27 '11 at 23:13
Thx this is great, I am going to use this open-source – David MZ Jun 28 '11 at 08:57
Not sure I would put my eggs in a basket that only about 50 other people are willing to use... but its your project. – CrazyDart Jun 28 '11 at 16:26
@CrazyDart - It's not really all your eggs in a basket. It's open source, keep a copy of the source for yourself if you like it. – vcsjones Jul 08 '11 at 03:47

score 5 · Answer 2 · answered Jun 27 '11 at 23:00

You should create a wrapper service called IFileService, then you can create a concrete that uses the statics for use in your app, and a mock IFileService that will have fake functionality for testing. Make it so you have to pass IFileService into the constructor or a property for what ever class is using it, this way normal operation requires you pass in the IFileService. Remember in Unit Testing you are testing just that part of code not the things its calling to like IFileService.

interface IFileService
{
    bool Exists(string fileName);
    void Delete(string fileName);
}

class FileService : IFileService
{
    public bool Exists(string fileName)
    {
        return File.Exists(fileName);
    }

    public void Delete(string fileName)
    {
        File.Delete(fileName);
    }
}

class MyRealCode
{
    private IFileService _fileService;
    public MyRealCode(IFileService fileService)
    {
        _fileService = fileService;
    }
    void DoStuff()
    {
        _fileService.Exists("myfile.txt");
    }
}

score 3 · Answer 3 · answered Jun 28 '11 at 09:23

See also Vadim's SystemWrapper. You can mock a lot of system classes with it, but you will need to apply the dependency injection pattern to make your code testable.

[Test]
public void Check_that_FileInfo_methods_Create_and_Delete_are_called()
{
    // Add mock repository.
    IFileInfoWrap fileInfoRepository = MockRepository.GenerateMock<IFileInfoWrap>();
    IFileStreamWrap fileStreamRepository = MockRepository.GenerateMock<IFileStreamWrap>();

    // Create expectations
    fileInfoRepository.Expect(x => x.Create()).Return(fileStreamRepository);
    fileStreamRepository.Expect(x => x.Close());
    fileInfoRepository.Expect(x => x.Delete());

    // Test
    new FileInfoSample().CreateAndDeleteFile(fileInfoRepository);

    // Verify expectations.
    fileInfoRepository.VerifyAllExpectations();
    fileStreamRepository.VerifyAllExpectations();
}

score 1 · Answer 4 · answered Aug 27 '13 at 01:02

I also used wrapper classes. I use this tool to easily generate wrapper classes such as System.IO.File

https://www.nuget.org/packages/Digitrish.WrapperGenerator/

Once you installed the package just type the following on Package Manager Console

Scaffold Wrapper System.IO.File

This will generate IFile.cs interface and one concreate wrapper class File.cs. Then you can use the IFile to Mock and File.cs for the real implementation.

score 1 · Answer 5 · answered May 19 '17 at 19:03

1

Why not using MS Fakes? Wouldn't that be simple, already supported compared to RhinoMocks, SystemWrapper.Wrapper and SystemWrapper.Interface?

answered May 19 '17 at 19:03

pixel

9,653
16
82
149

MS Fakes is a VS Enterprise-only feature, from what I understand. – Shafiq Jetha Dec 21 '17 at 19:16
1

Note that MS Fakes is available since VS 2012, he posted the question before that! There were MS moles before but not sure about its limits. – Bahadır İsmail Aydın Jan 25 '18 at 02:48

score 0 · Answer 6 · answered Jun 28 '11 at 05:45

0

In addition to the you can't mock Static easily answer.

I'd like to point out that you shouldn't be mocking File.IO type, because it is not a type that you own. You should only Mock types that you own.

answered Jun 28 '11 at 05:45

Gishu

134,492
47
225
308

score -1 · Answer 7 · answered Nov 05 '11 at 05:34

-1

You can use moq framework for this.It is open source google project which you can download from here. Download Moq framework

To get fully understanding about how to use moq with C# please refer the following article.

http://learningcsharpe.blogspot.com/2011/11/how-to-use-moq-library-for-your-unit.html

thanks, Erandika.

answered Nov 05 '11 at 05:34

Erandika Sandaruwan

183
2
11

1

Moq cannot test static classes, see http://stackoverflow.com/questions/12580015/how-to-mock-static-methods-in-c-sharp-using-moq-framework – guillem Apr 09 '13 at 21:27

Mock File IO static class in c#

7 Answers7

Linked